Respiratory syncytial virus (RSV) is an enveloped RNA virus that is the most important viral agent of pediatric respiratory tract disease worldwide. It currently lacks a vaccine or effective antiviral therapy. RSV is in Family Paramyxoviridae of Order Mononegavirales, the nonsegmented negative strand RNA viruses or mononegaviruses, and is the most complex member of the group. This large group of viruses includes important pathogens such as measles, mumps, rabies and Ebola viruses. Knowledge of the organization and expression of the RSV genome would help guide efforts to make attenuated recombinant viruses for use as vaccines, which is the major goal of related projects in this laboratory. It also would provide further insight into this important virus group. Previous studies identified the complete sequence of RSV genomic RNA and mapped its genes. We are continuing the analysis to characterize cis-acting signals in detail.